This invention relates to ignition systems for internal combustion engines and more particularly to one capable of providing two successive impulses of current to each spark plug during the power stroke of every four stroke cycle of the engine.
The conventional ignition system in an internal combustion engine is a device for conveying electrical current to the sparking plugs according to the firing order and is well known. Briefly, it comprises the contact-breaker with condenser, the ignition cam, the actual distributor and an automatic timing control device which determines the optimum ignition timing suited to the operating conditions of the engine.
The distributor has a longitudinal shaft whose lower end is connected to a drive pinion in the engine block. This shaft is rotated at the same speed as the camshaft of the engine and carries the ignition cam, which actuates the contact lever rotatably mounted on a plate. Fitted to the upper end of the shaft is the distributor rotor through which an electrode arm passes. The distributor cap is the cover of the housing. At the center, the cap is provided with a carbon brush through which the current is passed to the distributor rotor arm. At the edge of the cap are a number of electrodes, one for each cylinder of the engine. These electrodes are so arranged that the rotor arm is always at a contact just when the contact breaker interrupts the circuit of the primary winding of the ignition coil. At that instant a high voltage is induced in the secondary winding of the ignition coil, and this voltage is allowed to pass through the rotor arm to the appropriate sparking plug. The condenser prevents the occurrence of sparking at the contact breaker. The ignition spark is produced as follows: so long as the contact breaker has not been opened by the cam, current can flow in the primary circuit consisting of the battery, primary winding of the ignition coil, contact breaker and the earth; so that a magnetic field is formed in the ignition coil. At the instant when the contact interrupts the primary circuit, this magnetic field breaks down. This sudden change of the magnetic field induces a high voltage in the secondary winding, which voltage is thereupon applied to one of the sparking plugs, causing it to produce a spark.
The distributor housing also accommodates the timing control which automatically adjusts the optimum ignition timing, which largely depends upon the type of fuel and upon the load and speed of the engine at any particular time (e.g. idling or running under full load).
The aforementioned contact-breaker can be used to control the flow of a control voltage to a transistor or other solid state switching device which in turn controls the current supplied to the ignition coil. In addition, the control voltage to the solid state switching device can be controlled by various other means such as a magnetic pick-up coil sensing a projection or tooth on the distributor shaft in place of the conventional cam lobe, optical triggers employing a light emitting diode sensing slots in a disc carried by the distributor shaft, and various HALL EFFECT-type systems. The principles and teachings of the present invention are adaptable to any of the aforementioned voltage control means.
It is well known that timing control is very important to maximize power and reduce harmful exhaust emissions in the form of unburned hydrocarbon (HC), carbon monoxide (CO) resulting from too rich a fuel mixture or too little oxygen and various oxides of nitrogen (NOX) which when combined with unburned hydrocarbons react with sunlight to form smog. The arrival of current at the spark plug must be a precisely timed event that coincides with the air-fuel mixture being compressed to its maximum by the piston.
In theory, the spark should occur at the plug when the piston is at the very top of its travel in the cylinder also known as the top dead center (TDC) position and the air-fuel mixture is compressed to the maximum. Actually, a particular engine may perform better, either develop more power or lower exhaust emissions, if the spark occurs just slightly before top dead center (BTDC) or slightly after top dead center (ATDC). Normally, each spark plug is caused to fire before its associated piston reaches the top of its stroke which allows sufficient time for the expansion of the gases during combustion to drive the piston back down. However, frequently when the piston reaches the top of the power stroke, the air-fuel mixture flame or combustion is snuffed out prematurely in the combustion chamber. This phenomenon is especially noticed in the late model smaller engines of the two or four cylinders size.
The design of modern internal combustion engines has been changed in an attempt to reduce the aforementioned harmful emissions. For example, compression ratios have been lowered to reduce peak temperatures, combustion chambers have been modified to eliminate areas where combustion can be prematurely extinguished leaving a portion thereof unburned, camshafts have been changed to close exhaust valves early thereby permitting some exhaust gases to mix with the incoming fuel charge, and complex electrical ignition systems have been devised to provide more than the conventional single spark during the power stroke of the engine to name but a few.
Two armed distributor rotors for providing sparking current to various spark plugs at different strokes of the cycle for different cylinders are not new. U.S. Pat. Nos. 1,676,503 and 3,430,617 are examples of such rotors, however, as will be noted, the dual armed rotors do not provide dual ignition sparks for each power stroke of each cylinder as does the present invention.
The use of plural ignition sparks for each power stroke of the cycle for each cylinder is also not new. U.S. Pat. Nos. 3,554,178, 3,926,165 and 4,068,643 all show such a use, however, these devices employ complex costly electronic circuits, which are triggered by a conventional contact-breaker actuated by a single cam lobe for each cylinder or other means such as magnetic pickup systems or the like whereas the present invention teaches the use of two adjacent cam lobes for each cylinder as will be presently explained.
It is therefore the primary object of the present invention to provide a simple yet superior ignition system for internal combustion engines.
It is another object of the invention to provide such a system that is capable of providing two ignition sparks for each power stroke of a four stroke cycle engine.
It is another object of the invention to provide such a system which is adaptable to all present day electronic ignition systems.
It is another object of the invention to provide such a system which is effective, relatively inexpensive and requires no special skill to install or maintain.
It is another object of the invention to provide such a system by which substantial fuel economy can be realized, improved horsepower output and reduced harmful emissions are achieved as a result of the second ignition spark during each power stroke.
Other objects and advantages of my invention will be apparent and obvious from a study of the following description and accompanying drawings which are merely illustrative of the present invention.